Conventionally, as a coupler for connecting pipings to flow a fluid, there has been proposed various types.
Normally, the coupler has a structure as disclosed in Japanese Patent Application Laid-Open No. 2004-211818. That is, at a time when the pipings are not connected, at least one of ports is in a closed state so as to prevent a fluid from leaking to the outside. When the pipings are connected, the fluid can flow.
This is realized by providing a check valve to one side of the coupler and a pressure pin for pushing and opening the check valve to the other side of the coupler.
Further, there are provided a gasket for preventing the fluid from leaking to the outside at the time of connection and a lock mechanism for preventing the coupler from being easily detached.
On the other hand, by using a mechanical machining technique, there have been manufactured various types of pressure reducing valves.
The pressure reducing valves are broadly categorized into active drive type and passive drive type.
The active drive pressure reducing valve includes a pressure sensor, valve drive means, and a control mechanism, in which a valve is driven such that a secondary pressure is reduced to a set pressure.
Further, the passive drive pressure reducing valve has a structure in which when a set pressure is reached, by employing a differential pressure, the valve is automatically opened and closed.
Further, the passive drive pressure reducing valves are roughly categorized into pilot operated-type and direct acting-type.
The pilot operated-type pressure reducing valve has a pilot valve and is characterized by performing a stable operation.
The direct acting-type pressure reducing valve has an advantage with respect to a high-speed response. For the pilot operated-type pressure reducing valve, when a gas is used as a working fluid, in order to reliably perform opening and closing of a valve even with a minute force of a compressed fluid, a diaphragm is often used as a differential pressure sensing mechanism.
With regard to a small pressure reducing valve, for example, as disclosed in Japanese Patent Application Laid-Open No. 2004-031199, there is proposed a structure including a diaphragm, a valve body, and a valve shaft for directly connecting the valve body and the diaphragm to each other.
Known as a manufacturing method for the pressure reducing valve having the above-mentioned structure is a manufacturing method as disclosed in A. Debray et al, J. Micromech. Microeng., 15, S202-S209, 2005. The manufacturing method is characterized in that a semiconductor processing technique is employed to manufacture small mechanical components.
In the semiconductor processing technique, a semiconductor substrate is used as a material and a structure is formed by employing techniques such as film formation, photolithography, and etching in combination with each other.
Therefore, there are provided characteristics in which a fine processing of a submicron order is possible and a mass production is facilitated due to a batch process.
In particular, the pressure reducing valve has a complicated three-dimensional structure, so there are employed reactive ion etching (ICP-RIE) for vertically etching a semiconductor substrate and a bonding technique for bonding a plurality of semiconductor plates.
Further, a valve body and a valve seat are bonded to each other through an intermediation of a sacrifice layer of a silicon oxide or the like. In a latter half of a process, the sacrifice layer is etched, thereby allowing the valve body to be released from the valve seat.
On the other hand, as an energy source to be mounted on a small electrical equipment, a small fuel cell receives attention. A reason why the fuel cell is useful as a driving source for the small electrical equipment is that an energy amount which can be supplied per volume or per weight is several times to ten times that of a conventional lithium-ion secondary battery.
In particular, in a fuel cell for obtaining a large output, it is most desirable that hydrogen be used as a fuel.
However, hydrogen is gaseous at normal temperature, and a technique for storing hydrogen in a small fuel tank at high density is required.
Known examples of the technique for storing hydrogen include the following methods.
A first method is a method including compressing hydrogen to be preserved in a form of a high pressure gas.
When a pressure of the gas in a tank is 200 atmosphere, a volume hydrogen density is about 18 mg/cm3.
A second method is a method including maintaining hydrogen at low temperature to be stored in a form of a liquid.
In order to liquefy hydrogen, a large energy is required and the liquefied hydrogen is naturally vaporized to leak out, which is a problem. However, by this method, preservation at high density is possible.
A third method is a method including using a hydrogen storage alloy to store hydrogen.
In this method, a specific gravity of the hydrogen storage alloy is large, so, on a weight basis, there is a problem in that only about 2 wt % of hydrogen can be stored, thereby making the fuel tank heavier. However, on a volume basis, a hydrogen storage amount is large, so the third method is effective for downsizing.
In particular, in the small fuel cell, due to handleability and a large hydrogen charging amount per volume, there is often used the third method in which hydrogen is stored in a hydrogen storage alloy.
When all hydrogen in a fuel container is consumed by power generation, in order to continue the power generation, hydrogen is needed to be newly charged.
Replenishment of hydrogen can be performed in a state where a power generation portion of the fuel cell is kept connected to the fuel container. However, there is also a case where the replenishment is performed in a state where the fuel container is removed from the power generation portion.
This is because, while a pressure in the fuel container is high at the time of charging and it is desirable that the container be cooled at the time of charging, the pressure and a temperature history should be prevented from adversely affecting the power generation portion.
Further, also in view of convenience and economy, rather than possessing and carrying a plurality of fuel cells, it is desirable that only a plurality of fuel containers be carried, and, when a fuel container in use becomes empty, the fuel container be replaced with a new fuel container.
Thus, there is often employed a method in which a coupler is provided between the fuel container and the fuel cell power generation portion so that the fuel container becomes detachable.
As the coupler described above, as disclosed, for example, in Japanese Patent Application Laid-Open No. 2004-293777, there is proposed a coupler having a structure in which a plug and a socket can be separated from each other by an external force.
On the other hand, power generation of a polymer electrolyte fuel cell is performed as follows.
For a polymer electrolyte membrane, a perfluorosulfonic acid cation exchange resin is often used.
For example, for a film described above, Nafion manufactured by DuPont or the like is well known.
A membrane electrode composite, which is obtained by sandwiching the polymer electrolyte membrane between a pair of porous electrodes bearing catalysts such as platinum, that is, a fuel electrode and an oxidizer electrode, constitutes a power generation cell.
With respect to the power generation cell, by supplying an oxidizer to the oxidizer electrode and a fuel to the fuel electrode, proton moves in a polymer electrolyte membrane, thereby performing the power generation.
A polymer electrolyte membrane retaining a mechanical strength and normally having a thickness of about 50 to 200 μm is used in order to prevent a fuel gas from transmitting therethrough.
A strength of the polymer electrolyte membrane is about 3 to 5 kg/cm2. Accordingly, in order to prevent breakage of a film due to a differential pressure, it is desirable that the differential pressure between an oxidizer electrode chamber and a fuel electrode chamber of the fuel cell be controlled so as to be 0.5 kg/cm2 in a normal state or equal to or less than 1 kg/cm2 even in an emergency.
In a case where a differential pressure between the fuel tank and the oxidizer electrode chamber is smaller than the above-mentioned differential pressure, the fuel tank and the fuel electrode chamber are directly connected to each other and there is no particular need for pressure reduction.
However, in a case where the oxidizer electrode chamber is open to air and a fuel is charged at higher density, in a process of feeding the fuel from the fuel tank to the fuel electrode chamber, there is a need for pressure reduction.
Further, the above-mentioned mechanism is required also for stabilizing starting and stopping operation of the power generation and generated energy.
In Japanese Patent Application Laid-Open No. 2004-031199, a small valve is provided between the fuel tank and the fuel cell unit, thereby preventing the fuel cell unit from suffering breakage due to a large differential pressure, controlling starting and stopping of the power generation, and stabilizing the generated energy.
In particular, a diaphragm is used at a boundary between a fuel supply path and an oxidizer supply path, and is directly connected to a valve, thereby realizing a pressure reducing valve which is driven by a differential pressure between the fuel supply path and the oxidizer supply path without using electricity and which optimally controls a pressure of a fuel to be fed to the fuel cell unit.
Japanese Patent Application Laid-Open No. 2005-339321 proposes a dual valve-type pressure regulator having a structure in which a portion including a primary regulating valve and a portion including a secondary regulating valve are separated from each other and one of the portions is provided on the fuel tank side and the other thereof is provided on the fuel cell side, the portions being detachable from each other.